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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: kris on June 14, 2015, 11:12:38 AM
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Hi all,
I had a stellar out with my '86 K100. She was running like a top, as always. I park to visit a friend, go to start the bike and she feels like she's running on 3 cylinders. Check the spark plug leads...all good. This bike had a fresh fuel filter 400 miles ago, air filter good, battery new....this morning she won't even idle for me.
What can go wrong so fast to stop her dead in her tracks??
Any advice?
Thanks,
Chris
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the usual suspects are bad fuel... clogged fuel filter... bad fuel pump... bad fuel regulator... bad under tank fuel pump connection... bad jettronic connection... loose sparkplug... bad coil... loose spark plug wire... leaking rubber hoses... beyond that its gonna be temp sensor hes unit and the like...
if it were me i would be looking at the fuel filter and the under tank fuel pump connection and the jettronic connection... the fuel filter is easy to remove and blow through... the connectors are easy to clean and exclude...
i have had the under tank fuel pump connection cause all kinds of whack... once i replaced it with a 4 way trailer connector all my whack went away...
once i filled up with chevron supreme with techron at a tiny joint out in the wilderness... once at my destination i had problems starting and keeping it running the next day... i pulled the fuel filter and could barely blow through it... being suspect of tiny outta the way gas stations... i decided to replace the fuel filter which had replaced 2 weeks prior and fill up with fresh gas... the problems immediately went away...
j o
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fouled plug usually the culprit on mine, but it's a 750 and they're notorious for that.
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Hi Johnny,
Thanks for your prompt reply. My fuel is super fresh. I run Heinz every other day and this is the first hint of a problem. Just checked the inside of the tank. Everything is spanky clean, pump hums, connections good. Unplugged and re-connected the 4 pin connector from the tank (I'm assuming that's what you're talking about). The only thing I did (and I don't think it's relevant) is put a little Marvel Mystery Oil in the tank before topping her up and heading out for the 25 mile run to St. George. Honest to God, smiling all the way thinking what a great bike this is! The fuel filter is the alternate NAPA part (if I recall) that guys talked about on the blog. All four exhaust pipes are hot from the little bit of chugging I could get her to do. Jetronic was DEOXIT sprayed on re-assembly but will pull it and try again. The HES is unknown territory to me.
I will try a fresh filter if all else fails. Man, that would be odd, though....consider Heinz had been running on her original filter for 20 plus years!! There is huge volume at the stations I get gas from so it ain't bad fuel...
Was saying to myself I would take the Beemer over my newer Concours for a planned trip to Halifax but this has me wondering! I have put just under 700 miles on her since the snow melt all the while considering these test rides to see how she does. Hiccups are to be expected but I don't like 'em!
Thanks again for getting back so quickly. Hope all is well in Cheezkonzin!
Chris
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Thanks Chaos. Fresh plugs 700 miles ago but I'll check 'em.
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they want to be ridden long and hard... its the best thing to avoid whack...
i had a looose #1 plug once... had all kinda whack with starting and idling till i found that little piece of evil...
id ride a couple back to back full tanks of no corn ethyl through it with a 1/2 a 20oz bottle of techron in each tank and skip the marvel mystery oil... it just needs to be ridden...
are you telling us everything about this moto... last work done other than what you already stated...
j o
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I hear ya' and I agree. Ride those damn bikes. Don't leave them to rot in a garage...can't seem to find Techron north of the 49th. I wonder if an injector might have gone funny. Without so much as a hint of warning I always think electrical. The spinning bits will often give you a small warning, in my experience. The rubber is good. Funny you should mention temp sensor because I have yet to hear the fan come on, even though it was bench tested and ran fine. Can an FPR stick or go funky and cause this sort of thing?
Here's to no more "whack"!!
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Just tried her again. She won't respond to either full throttle advance (choke) or to throttle. She starts with half advance sounding just ok and then sputters and dies. I am getting some phantom readings from the speedo which I don't ever recall seeing before.
Frustrating...
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Geez, I feel odd replying to my own posts!! But I had a thought. I think the issue with Heinz is the MAF. If the flapper were stuck in the wrong position could this cause the rough start and die problem.....along with no throttle response? When I pulled the plugs they seemed a little wet. I'm guessing the flapper is stuck open and the bike is, therefore, getting too much fuel and the throttle not responding because it thinks it's already getting enough? Does that make sense? The flapper had been clanging on deceleration for as long as I owned her. I've read that the bushings can wear and cause the flapper to stick. I'll check it and re-post. Never a dull moment in Old Beemerville!
PS - this would explain why it happened so suddenly
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Der Heinz ist wieder wohl!! (that means my bike is better now....roughly). It was a leak at the fuel pump output fitting that was the culprit. I had repaired the snapped off fitting with JB Weld thinking that might do it (even though I had a new pump in hand....thought I'd keep that as a spare). It didn't. It ran well for 700 miles and then the issue popped up. So it seems that inadequate fuel pressure can muck things up in a hurry. The bike ran like it was running on 2-3 cylinders, although all four were firing, wouldn't take any throttle, and didn't like the throttle advance. I offer this in the event anyone else has similar symptoms. Could be that you have a fuel line leak within the tank...and how would you know...since the pump is running fine, there is no external sign of fuel leaking, etc.. Don't be afraid to check it out.
Good luck all and, as always, thanks for the support and suggestions.
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greetings kris...
im not seeing where you told us about the jb weld fuel pump fix in your original post...
am i whack for not seeing it... or... are you whack for not saying it...
j o
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Howdy Johnny, from the eastern shores of Lake Huron. I did not mention the fix since I didn't think it had bearing. So, no, you are not whack. And I don't think I'm whack...although my wife and kids might disagree! All good now....at least until the next episode.
Always good to know that I have my brothers of the brick to consult with.
Best,
Chris